1. Field of the Invention
The present invention relates to an electromagnetically-powered valve operating apparatus of an automotive internal combustion engine which is capable of electromagnetically operating intake and exhaust valves.
2. Description of the Prior Art
In recent years, there have been proposed and developed various automotive valve operating apparatus each of which has electromagnetically-operated valve units for electromagnetically opening and closing intake and exhaust valves. Such automotive valve operating apparatus having electromagnetically-operated valve units have been disclosed in Japanese Patent Provisional Publication Nos. 61-247807, 7-324609, and 9-256825.
Opening and closing actions of an exhaust valve tend to be both affected by residual in-cylinder pressure, still remaining in the combustion chamber when opening the exhaust valve at the end of the combustion stroke and when closing the exhaust valve at the end of the exhaust stroke. On the other hand, only an intake pressure having a comparatively low pressure level acts on an intake valve. From the viewpoint discussed above, the inventor of the invention discovers that it is desirable to downsize only an electromagnetically-operated intake-port valve unit in comparison with an electromagnetically-operated exhaust-port valve unit. Hitherto, a specification (size and type) of an electromagnetically-operated intake-valve unit and a specification of an electromagnetically-operated exhaust-valve unit were identical to each other, thus increasing the total size of an engine cylinder head in a vertical direction of the engine as well as in a direction of its width. As a result, an engine-hood line must be designed to be higher. This reduces design flexibility in a limited space of the engine. Also, the electromagnetically-operated intake-valve unit uses the same large-sized electromagnetic coils as the electromagnetically-operated exhaust-valve unit, thereby resulting in an increase in electric-power consumption.
Accordingly, it is a principal object of the invention to provide a valve-operating apparatus of an automotive internal combustion engine having electromagnetically-operated valve units, which avoids the aforementioned disadvantages of the prior art.
It is another object of the invention to provide a small-sized valve-operating apparatus of an automotive internal combustion engine having electromagnetically-operated valve units, which can compactly design in the vicinity of a cylinder head, and reduce electric-power consumption.
In order to accomplish the aforementioned and other objects of the present invention, an electromagnetically-powered valve operating apparatus of an internal combustion engine of an automotive vehicle, comprises a first valve operating unit adapted to be connected to an intake valve located in a cylinder head, the first valve operating unit comprising a first flanged plunger connected to a valve stem of the intake valve and having a flanged portion, a first pair of electromagnetic coils respectively facing to both faces of the flanged portion of the first flanged plunger, and a first pair of coil springs permanently biasing the valve stem of the intake valve respectively in a direction opening the intake valve and in a direction closing the intake valve, the first pair of coil springs cooperating with the first pair of electromagnetic coils for electromagnetically opening and closing the intake valve by electromagnetic force plus spring bias, a second valve operating unit adapted to be connected to an exhaust valve located in the cylinder head, the second valve operating unit comprising a second flanged plunger connected to a valve stem of the exhaust valve and having a flanged portion, a second pair of electromagnetic coils respectively facing to both faces of the flanged portion of the second flanged plunger, and a second pair of coil springs permanently biasing the valve stem of the exhaust valve respectively in a direction opening the exhaust valve and in a direction closing the exhaust valve, the second pair of coil springs cooperating with the second pair of electromagnetic coils for electromagnetically opening and closing the exhaust valve by electromagnetic force plus spring bias, wherein the first valve operating unit is relatively down-sized in comparison with the second valve operating unit, so that a spring height of each of the first pair of coil springs is set at a smaller value by setting a spring bias of each of the first pair of coil springs at a lower value than each of the second pair of coil springs, and so that a coil outside diameter and a coil height of each of the first pair of electromagnetic coils are both reduced by reducing a number of turns of each of the first pair of electromagnetic coils and by weakening a magnitude of electromagnetic force created by each of the first pair of electromagnetic coils in comparison with each of the second pair of electromagnetic coils.
According to another aspect of the invention, an electromagnetically-powered valve operating apparatus of an internal combustion engine of an automotive vehicle, having an intake valve and an exhaust valve located in a cylinder head so that a valve stem of the intake valve and a valve stem of the exhaust valve are set at an angle, comprises an intake-valve side valve operating unit adapted to be connected to the intake valve, the intake-valve side valve operating unit comprising a first flanged plunger connected to the valve stem of the intake valve and having a flanged portion, a first pair of upper and lower electromagnetic coils respectively facing to both faces of the flanged portion of the first flanged plunger, and a first pair of upper and lower coil springs permanently biasing the valve stem of the intake valve respectively in a direction opening the intake valve and in a direction closing the intake valve, the first pair of upper and lower coil springs cooperating with the first pair of upper and lower electromagnetic coils for electromagnetically opening and closing the intake valve by electromagnetic force plus spring bias, an exhaust-valve side valve operating unit adapted to be connected to the exhaust valve, the exhaust-valve side valve operating unit comprising a second flanged plunger connected to the valve stem of the exhaust valve and having a flanged portion, a second pair of upper and lower electromagnetic coils respectively facing to both faces of the flanged portion of the second flanged plunger, and a second pair of upper and lower coil springs permanently biasing the valve stem of the exhaust valve respectively in a direction opening the exhaust valve and in a direction closing the exhaust valve, the second pair of upper and lower coil springs cooperating with the second pair of upper and lower electromagnetic coils for electromagnetically opening and closing the exhaust valve by electromagnetic force plus spring bias, wherein the first valve operating unit is relatively down-sized in comparison with the second valve operating unit, so that a spring height of each of the first pair of upper and lower coil springs is set at a smaller value by setting a spring bias of each of the first pair of upper and lower coil springs at a lower value than each of the second pair of upper and lower coil springs, and so that a coil outside diameter and a coil height of each of the first pair of upper and lower electromagnetic coils are both reduced by reducing a number of turns of each of the first pair of upper and lower electromagnetic coils and by weakening a magnitude of electromagnetic force created by each of the first pair of upper and lower electromagnetic coils in comparison with each of the second pair of upper and lower electromagnetic coils.